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Monitoring the Performance of Your Network

In one sense, you already have an army of network monitors in your library. Every time something goes wrong, you probably get a few spontaneous alerts from patrons and colleagues. However, if you want preventive information and in­-depth analysis of what’s happening on your network, you need network monitoring software.

Why Should You Monitor the Traffic on Your Network?

You can get information about the health of your network. If a server stops responding, or your ILS crashes or a segment of your network goes offline, the network monitor will send you a message so you can respond right away. But these tools go beyond reactive alerts about things that are already broken. They can also provide warnings about network slowdowns, overloaded servers and other signs of trouble so you can address problems before they affect staff and patrons.

Better understanding of long­-term trends. Network monitoring tools also create graphs and reports about network performance over time. How fast is the demand for bandwidth growing in your library? If your library’s average daily Internet use has grown 1 Mbps (megabits per second) over the past six months, you can get a rough sense of how much you’ll need three years from now and budget accordingly. You can also plan better for the replacement of servers, switches and routers, because network monitors keep statistics related to performance of these devices.

Improved ability to check on your ISP. Life would be much easier if we could just trust our ISPs. You’re paying for a 1.5 ­Mbps T­-1 connection, and that’s what you’re getting, right? No need to worry about measurements and monitoring. Just let the ISP tell you whether they’re doing a good job and when it’s time to upgrade. If you’re a little less trusting, a network monitor can keep track of uptime and other metrics on your Internet connection, so you’ll know when your ISP is failing to maintain its promised level of service.

Key Actions

Get permission. Be sure you contact your network administrator before you install any network monitoring software or equipment. If mis-configured, a monitoring tool could flood the network with unnecessary traffic.

Ensure compatibility. Check to see that the network monitoring tool you’re interested in can communicate with your existing equipment. There are different network management protocols (e.g., Simple Network Management Protocol, or SNMP, and Cisco’s Netflow), and your routers, switches and servers might not recognize the protocol used by your monitoring tool.

Create network diagrams. Most network monitoring software can automatically create a diagram of your local area network and/or your wide area network. Even if you decide not to use a monitoring tool, it’s a good idea to create a network diagram using software such as Microsoft Visio or Gliffy, or drawing it out by hand.

Network Performance Metrics

Bandwidth, throughput and speed are three terms that most people use interchangeably when discussing networks. However, speed isn’t really accurate in this context (though it is used all the time anyway), and there is a small distinction between bandwidth and throughput, as discussed in the following section. Latency and jitter are two connected concepts that increase in importance as more people conduct real-­time voice and video interactions across the Internet. Uptime is another important metric that’s a little easier to understand.

Network Monitors and Other Utilities

Ping, traceroute and speedtest sites are quick, easy-­to-use troubleshooting tools, but they don’t provide in-­depth information or analysis. For example, a speedtest site doesn’t take into account the fact that you’re sharing bandwidth with colleagues and patrons. If the speedtest indicates that you’re on a 200-­Kbps connection, even though you’re paying your ISP for a 1.54­ Mbps T-­1 line, the slowdown is probably due to other library patrons.

Also, even when you’re the only person on the local network, your Internet connection carries a lot of administrative overhead (i.e., bits passed back and forth between computers to set up and tear down a connection). Therefore, you might see a reported throughput of 1.2 Mbps instead of the full 1.54 Mbps you were expecting.

This is normal, but if you want a fuller picture of what’s happening on the network, install one of the network monitoring programs mentioned next. Also, be sure to ask your network administrator before you install any monitoring software.

Ping and traceroute: If you want a quick snapshot of the latency on your network, use ping, a command-­line tool built into all Windows PCs (and most other machines as well). When you ping a remote IP address, you’ll see four replies, and each one includes the “time” (measured in milliseconds) it took for your ping request to reach the remote computer and then return to your PC. In other words, you’re looking at the latency on the network between your computer and the remote computer. To be more specific, you’ve measured the round­-trip latency. If you want the one­-way latency, cut the ping time in half. Traceroute (or Tracert on Windows machines) is a similar tool that provides information about latency. Also, both tools are commonly used for basic connectivity troubleshooting.

Speedtest.net: Speedtest is a free site that measures latency, upstream throughput and downstream throughput with a single click. Furthermore, you can measure these between your location and several hundred servers around the world. In other words, latency between your library and the nearest city will usually be much lower than the latency between your library and London. Throughput will also vary widely, depending on the server you try to access. Speakeasy also has a speed test, as do several other sites.

Network monitoring software: The ping utility and the online speed tests have a serious drawback. You’ll only get a quick, unrepresentative view of your network’s performance, unless you plan to spend all day at the command prompt sending ping messages out to various computers. Network monitoring software gathers information about your network at regular intervals and grabs your attention only when there’s a problem or an event that you want to know about. For example, if your main file server is almost out of hard drive space, the server sends a message to the network monitoring tool, which, in turn, sends you an email or finds another way to alert you of the problem.

You definitely want reports from your border router about the total amount of Internet traffic you’re sending and receiving on a daily, monthly and yearly basis. Look at both the average load and the peak load, and you’ll have a better sense of how quickly demand is increasing. If your average daily load is consistently above 60 percent and your peak load is consistently above 80 percent (for an hour or two per day), you’ve probably noticed some slowing already and heard about it from your end users. If you’re approaching those numbers, you should start planning for an upgrade. Or you should invest in bandwidth management technology.

Also, most network monitoring tools include graphing and charting components, which let you see the long-­term trends in your library. How fast are the hard drives filling up on your file servers? What’s the average daily throughput on your Internet connection compared to this time last year? Understanding the rate of change lets you budget accurately, and it gives you early warning so you have the right equipment on hand when it’s needed.

Popular open­-source or free monitoring tools include OpenNMS, Nagios, Cacti, Spiceworks, MRTG and PRTG (in rough order from most complicated to least complicated). Also, there are several dozen commercial vendors in this field, and you can find a product comparison chart at Wikipedia.

Stories from the Field

It’s pretty obvious, I think, when you’re really running out of space or out of bandwidth, and we are right now for sure. But we also have a tool called PRTG that monitors bandwidth and the network connections. You need to do that, especially if you’re using your network like we are, where we’re doing security cameras, Voice over IP, data and HVAC controls. We’re doing a lot of stuff over the network connection. So it’s critical that it work properly.

Jim Haprian
Medina County Library, OH

Further Resources

For more information about network performance monitoring and metrics, check out the Further Resources section.